Hazardous phosphor-gypsum chemical waste as a principal component in environmentally friendly construction materials

Phosphor-gypsum (PG), lime production and gold mining wastes were used to fabricate solid bricks. The PG waste had a high content of heavy metals and a pH value near 13. The purposes of this research were to develop new composites from these wastes; to research the physicochemical processes of developed materials structure formation. The representative samples were supplied by local Brazilian plants. The PG waste had a high content of heavy metals and a pH value near 13. The chemical and mineralogical compositions of the raw and final materials were studied by complex of complementary methods: XRD, XRF, SEM, EDS, AAS and LAMMA methods. Developed materials exhibited axial strengths of 8.3 MPa on the 3rd curing day and of 13.7 MPa on the 365th day. After 28 days, the water resistance coefficient was 0.95, the water absorption ranged from 9.2% to 17.5%, the shrinkage was 0.75% and the leaching and solubility levels of heavy metals were very low. These values meet the demands of Brazilian materials like bricks, blocks, etc. It was determined, that mainly amorphous new formations are responsible for the materials strengthening. The biggest benefit of the developed materials produced at the industrial level is the environmental protection.